Electron discharge device



March 22, 1938. Y RoTHE ET-AL Y 2,112,050

' "ELEGTRON DISCHARGE DEVICE Filed Sept. 18, 1956 Hor Em v WERNER KLEEN www Patented Mar. n, 1938 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE Application September 18, 1936, Serial No. 101,380 In Germany October 8, 1935 SCIaims.

Our invention relates to electron discharge devices and particularly to such devices intended for use at high frequencies. 1

In the methods used at the present by the prior art for the control in amplier tubes of electron currents, the electrons are influenced by the control eld in a state wherein they have a relatively small velocity. This means that the electrons are for a relatively long time in the controlling alternating ileld. Also in transmitter tubes, cathode ray tubes and so forth, the control is effected in a zone of the discharge space wherein the electron speed is small. Special measures such as retarding electrodes have also been used in order to render the electron speed within the control range equal to zero. 'Ihis was due' to the supposition that for the control of slowly moving electrons a small control potential was suiicient. However, the following relationships were not taken into consideration: If the time of transit of the electrons approaches the duration of the period of the alternating potential impressed, the electrons will absorb energy from the coupled circuits connected to the electrodes, and that there appears in these circuits attenuation phenomena which render the selective qualities poorer, that is, reduces the selectivity. For instance in high-frequency amplifier tubes, a loading of the tuned input circuit results.

The principal object of our invention is to provide an improved electron discharge device intended for use at high frequencies.

'I'he invention is based upon the consideration that it is necessary for the elimination of the disadvantages above enumerated to render the time of transit of the electrons as short as possible in the control eld. This is accomplished in accordance with the invention in that the electrons are inuenced at such places where they still have high velocity, in contrast to the method used by the prior art. Hence, in this manner, the influence of the controlling eld on the individual electron lasts a very'short time only and the result is that a detrimental attenuation of the control circuit and a. flattening out of its resonance curve is avoided.

The novel features which we believe to be characteristic of our invention are set forth with particuiarity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a diagrammatic representation of an electrode system illustrating our invention; Fig. 2 shows characteristic curves for the electrode system' (Cl. Z-27) shown in Fig. 1; Fig. 3 is a. ditic representation of an electron discharge device made according to our invention and Fig. 4 is a diagram illustrating one condition of operation of an electron discharge device made according toour invention.

The idea of the invention will now be explained with the aid of a few examples. In Fig. 1 the auxiliary electrodes are shown at I and I'. The control grid H of the amplifier tube has disposed behind it the plate III. The potential of electrode I is designated by p1, and the effective potential in the control grid area by pz. The electrons enter the field existing between electrodes I and II at an angle of inclination u with respect to the direction of the eld. If this ield is retarding, the electrons move on parabolic paths, as shown for instance by the dashes. A simple calculation shows that the electrons can only reach the control grid area II and thus also plate III if the eii'ective potential of the control grid area is This formula points out that the velocity with which the electrons are retarded during the control action depends essentially on the size of angle a. If for instance, the electrons enter the field at angle a equal to zero, they must be retarded for the control down to zero speed. On the other hand, if it is assumed that angle a=45 and that the potential p1 of the auxiliary electrode I=l00 volts, the apex of the parabolic electron paths is then located on a potential plane of about 50 volts. Hence, the electrons can reach the area of control grid H and plate DI only when the eiective potential pa of the control grid II is 50 volts and are then retarded only down to a speed of 50 volts in the direction in which they are traveling. As long as the eiiective potential pz of the control grid is 50 volts, the electrons return to auxiliary electrode I, or they are taken up by auxiliary electrode I' whereby they are however again retarded only to 50 volts.

'I'he discharge characteristic which results from electronic radiation composed of electrons of equal speed and parallel direction, is shown in Fig. 2 by curve a. It may be seen, that the control takes piace therefore with relatively high electronic speed and that the electrons do not stay very long in the control iield. If the electron beam has a certain angular deviation Aa at the entrance in the retarding eld, the characteristic assumes the form of curve b in Fig. 2. 'I'his is due to the fact that to the electrons entering the control eld under diilerent angles there must be coordinated elective potentials of diherent sise at the control grid in order to cause them to return. 'Ihe rounding oi the character istie takes place between the potential values ps=p1.sin(atAa (2) The form of characteristic shown in Fig. 2 is entirely novel, for in all characteristics known up to the present in the prior art the discharge current starts with the effective potential of the control grid. Hence these characteristics are evolved under the assumption that the control inhuences those electrons which are retarded down to very small speeds. The characteristics shown in Fig. 2 start only with positivel eiIective potentials and move the more in the direction of positive ehective potentials the larger is chosen the angle of incidence a, that is the faster the electrons that are used where they are turned back.

As shown by Formula 1, there exists a relationship between the size of the eiIective potential ,n at the control grid electrode required for the control of the electron beam and the angle of incidence a oi the electron rays. From this it may be seen that the control can be accomplished by variation of the intensity of the controlling held, as well as by inhuencing the effective potential pz, or then again by variation of angle e. In certain cases the simultaneous use oi both controls might come in consideration. In both cases the means known forv intensity control or angular control of discharge currents may be employed, for angular control magnetic as well as electrostatic dehection helds can be brought to act.

The electrode arrangement shown in diagrammatic manner in Fig. 1 is solely to serve for an explanation of the idea of the invention. Fig. 3 shows the cross-section through an electrode system suitable for the practical -application of the idea of the invention. From the hot cathode K electrons move through grid-like electrode I (potential ai) outwards and are parted into two bundles or beams, B, B' by rods 3 charged with cathode potential. If for instance electrode 5 is also impressed with the potential [n a characteristic is obtained with the variation'of the potential of electrode 4 whose course coincides with the one of the characteristics b of Fig. 2. The electron current is distributed in this case between electrodes 4 and 5. 'I'he steepness of the characteristic depends Ion the size of the angle oi divergence with which the electrons enter the retarding held of the control space.

If it is desired to make the steepness of the discharge characteristic as great as possible it is necessary to make this angle of divergence which was given the symbol Aa previously as small as possible. To achieve this there are basically two possibilities:

1. The electrons are sharply focused into beams so that the electrons move in parallel paths and enter a homogeneous decelerating held at a dehnite angle a of dehnite sense.

2. With insuhlcient focusing of the beam, that is where the electrons leave the cathode in various directions and move therefore in diverging paths, the retarding held can be shaped so that all electrons enter the held at the same angle.

'I'he second case is shown in Fig. 4. Here the electrons of various courses enter a decelerating held of such curvature that they pass through the same equi-potential area P, P', P" at the same angle a. This again has the result that the electrons return on the same potential area. practically speaking, that is reach the control area with the eiiective potential of the latter being equal for all electrons and thus they reach the anode.

While we have indicated the preferred embodiments oi our invention of which we are now aware and have also indicated only one specific application for which our invention may be employed, it will be apparent that our invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims.

What we claim as new isz- 1. The method of controlling a discharge current in an electron discharge device having a source of electrons, control electrodes and ananode, and comprising establishing an electric control held between said control electrodes and said anode a portion of said held having a retarding characteristic, applying an alternating potential to one of said control electrodes, ard causing electrons to pass through said electric control held at an angle with respect to the direction oi' the held in a period of time small compared to the period of said alternating potential.

2. The method of controlling a discharge current in an electron discharge device having a source of electrons, control electrodes and an anode, and comprising establishing an electric control held between said control electrodes and said anode, applying an alternating potential to one of said control electrodes,and causing electrons to enter said electric control held at an angle with respect to the direction oi the held and topass through 'said electric control held in a period oi time small compared to the period of said alternating potential.

3. 'Ihe method of controlling a discharge current in an electron discharge device having a source of electrons, control electrodes and an anode, and comprising establishing an electric control held between said control electrodes and said anode a portion oi.' said held having a retarding characteristic, applying an alternating potential to one of said control electrodes, and causing electrons to pass through said electric control held at an angle with respect to the direction of said held in a period oi' time small compared to the period of said alternating po,

tential, and controlling said electrons by varying the intensity of the electric control held.

4. The method of controlling a discharge current in an electron discharge device having a source of electrons, control electrodes and an anode, and comprising establishing an electric control held between said control electrodes and said anode, applying an alternating potential to one of said control electrodes, and causing electrons to pass through said electric control held, and controlling said electrons by varying the angle of incidence between said electrons and the direction of the electric control held to cause said electrons to pass through said electric control held in a period of time small compared to the period of said alternating potential.

5. The method of controlling a discharge current in an electron discharge device having a source oi' electrons, control electrodes and an anode, and comprising establishing an electric control held between said control electrodes and said anode, applying an alternating potential to one of said control electrodes, and causing electrons to pass through said electric control ileld at an angle to the direction of the field and simultaneously varying the intensity of the control ileld and the angle of incidence between the electrons and the control eld to cause said electrons to pass through said electric control eld in a period of time small compared to the period of said alternating potential.

6. The method of controlling a discharge cur-- source oi.' electrons, control electrodes and an anode, and comprising establishing homogeneous electric control field between said control electrodes and said anode, applying an alternating potential to one ot-said control electrodes, and focusing said electrons into concentrated beams to pass through said homogeneous control iield.

8. The method of controlling a discharge current in an electron discharge device having a source ,of electrons, control electrodes and an anode, and comprising establishing an electric control eld between the control electrodes and the anode, applying an alternating potential tn one of said control electrodes and causing said electrons to enter said electric control-held in diverging paths and forming s aid electric control iield so that the potential areas are curved to cause all the electron paths to pass through equivalent equipotential areas at the same angle but diilering from 90.

HORST ROTHE.

WERNER KLEEN. 

